DNS zone for internal net

[moseley@hank.org]

I moved my internal machines from static IP assignment to DHCP.  I use 
"host" sections with MAC addresses in dhcpd.conf, so the machines still get 
the same IP assingments.

I don't want to maintain hosts files on the internal machines for listing
other machines in the internal network, so I'd like to use Bind for
resolving IPs on the internal network.

I'm running Bind9 on the machine that is doing NAT for the internal LAN.  It
provides public DNS lookups for my public machines.  Of course I don't want
to add private IPs to the zone that lists the public IPs. 

I suppose one solution would be to create a subdomain and then add a zone 
for that subdomain (that only allowed DNS queries from the internal LAN).  
But then outgoing mail from the internal LAN might use the subdomain which.

I'm sure this is a common setup with a better solution.

Thanks,